Detailed analysis of structures and formulations of cationic lipids for efficient gene transfer to the lung

Effects of Microtubule-Depolymerizing Agents on the Transfection of Cultured Vascular Smooth Muscle Cells: Enhanced Expression with Free Drug and Especially with Drug–Gene Lipoplexes

The microtubule-depolymerizing agents colchicine, vinblastine (VB), vincristine, nocodazole, and podophyllotoxin were found to increase dramatically the transfection of cationic phospholipid-DNA (CMV-beta-gal) complexes on cultured vascular smooth muscle cells (VSMCs). Pretreatment of cells with free colchicine before addition of lipoplexes increased transgene expression both in the presence and in the absence of serum. Free vinblastine had similar effects; however, vinblastine was more effective (approximately 30-fold maximal stimulation) when incorporated into the lipoplexes. Under optimal conditions, vincristine, nocodazole, and podophyllotoxin produced 25- and 39-, 31- and 14-, and 26- and 14-fold increases in the absence and presence of serum, respectively. Taxol, which stabilizes microtubules, had no effect on transfection, but it blocked the positive effect of colchicine. Cytochalasin B, which inhibits microfilament polymerization, had no effect on transgene expression. By fluorescence microscopy, normal lipoplexes colocalized with lysosomes. In contrast, there was little, if any, colocalization of VB lipoplexes with lysosomes. Because depolymerization of microtubules induces NF-kappaB-dependent gene expression, the effects of pyrrolidinedithiocarbamate and Nalpha-p-tosyl-L-lysine chloromethyl ketone, inhibitors of NF-kappaB activation, were tested; inhibition of vinblastine stimulation of transfection was 85 and 66%, respectively. Also, immunofluorescence microscopy showed that vinblastine induced the translocation of NF-kappaB from the cytoplasm to the nucleus. It is concluded that microtubule-depolymerizing agents, especially when incorporated into lipoplexes, dramatically increase transfection of VSMCs, probably by two mechanisms: (i) inhibition of transport of lipoplexes to lysosomes and (ii) activation of transcription (via NF-kappaB). There have been some reports on the use of pharmaceutical agents to enhance gene expression, but generally these have involved separate applications of drug and gene. The ability to deliver a drug and a gene in a single therapeutic formulation could have significant clinical implications.

Enhanced Intravenous Transgene Expression in Mouse Lung Using Cyclic-Head Cationic Lipids

Herein, we report enhanced intravenous mouse lung transfection using novel cyclic-head-group analogs of usually open-head cationic transfection lipids. Design and synthesis of the new cyclic-head lipid N,N-di-n-tetradecyl-3,4-dihydroxy-pyrrolidinium chloride (lipid 1) and its higher alkyl-chain analogs (lipids 2-4) and relative in vitro and in vivo gene transfer efficacies of cyclic-head lipids 1-4 to their corresponding open-head analogs [lipid 5, namely N,N-di-n-tetradecyl-N,N-(2-hydroxyethyl)ammonium chloride and its higher alkyl-chain analogs, lipids 6-8] have been described. In stark contrast to comparable in vitro transfection efficacies of both the cyclic- and open-head lipids, lipids 1-4 with cyclic heads were found to be significantly more efficient (by 5- to 11-fold) in transfecting mouse lung than their corresponding open-head analogs (5-8) upon intravenous administration. The cyclic-head lipid 3 with di-stearyl hydrophobic tail was found to be the most promising for future applications.

Cationic corticosteroid for nonviral gene delivery

Delivery of plasmid DNA for gene therapy often provokes an inflammatory response that reduces transgene expression. Cationic lipids for lipofection lack pharmacological activity despite the hydrophobicity of many drug candidates that could be exploited. We report a one-step synthesis of a water-soluble, dexamethasone-spermine (DS) cationic lipid that has potent gene transfer capability in confluent endothelial cells when used with the neutral lipid, dioleoylphosphatidylethanolamine (DOPE). In contrast, unconjugated mixtures of dexamethasone, spermine, and/or DOPE have essentially no gene transfer activity. DS retains partial corticosteroid character as quantified by the rapid translocation of glucocorticoid receptor to the nucleus and by dose-dependent transactivation from a glucocorticoid response element. DS has anti-inflammatory activity in vivo in the mouse thioglycollate model of inflammation. In a mouse lung model, DS:DOPE resulted in significantly less interferon-gamma production at Day 1 and elevated transgene expression at Days 1 and 7 postintranasal instillation compared to DC-Chol:DOPE (sterol:DOPE:phosphate molar ratio of 1:1:1). Cationic pharmacophores such as DS represent a new approach to gene delivery and localized therapy.

Compositional effects of cationic lipid/DNA delivery systems on transgene expression in cell culture

Studies of the contribution of various physical properties of cationic lipid/DNA complexes (CLDCs) to their observed transgene expression in vitro were conducted using cationic liposomes composed of the cationic lipids 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) and dimethyldioctadecylammonium bromide (DDAB), with or without equimolar amounts of cholesterol (CHOL) or 1,2-dioleoylphosphatidylethanolamine (DOPE). The relative degree of luciferase expression by CLDCs is dependent on a complex relationship between net charge of the CLDC as well as previously reported properties, such as membrane fluidity and curvature of the cationic bilayer. Assessments were made of the role of these physical properties on CLDC stability in the extracellular medium, the extent of DNA cellular association, and membrane disruption activity. The efficiency of luciferase expression from negatively charged CLDCs is greatly improved by incorporation of DOPE. This result correlates with enhanced resistance to inhibition of gene delivery by heparan sulfate, increased cellular association of DNA, and enhanced membrane disruption activity. Luciferase expression by positively charged CLDCs is greatly reduced by incorporating equimolar amounts of CHOL and DOPE. This result occurs is in spite of increased resistance to heparan sulfate-mediated inhibition of gene delivery, increased DNA cellular association, and enhanced membrane disruption activity. The observed CLDC compositional effects on luciferase expression along with observed effects on the delivery process suggest that a better understanding of the kinetics and specific routes of gene delivery is necessary.

Poly (D, L-lactide-co-glycolide)/DNA microspheres to facilitate prolonged transgene expression in airway epithelium in vitro, ex vivo and in vivo

Repeat administration of gene therapy for cystic fibrosis is likely to be essential for long-term clinical efficacy. This may be minimized by the use of slow-release gene transfer preparations with more prolonged expression and longer dosing intervals for the patient. Poly(D-L-lactide-co-glycolide) (PLG) is a biodegradable and biocompatible polymer that has been used to encapsulate plasmid DNA. PLG-DNA microspheres were generated and characterized with respect to morphology, size (80% of particles <5.2 microm), and encapsulation efficiency (50.7+/-2.3%, n=6). Gel electrophoresis of DNA re-extracted from the microspheres confirmed that despite a decrease in the proportion of supercoiled conformation, it had not been degraded by the preparation process. Gene transfer efficiency was tested using microspheres encapsulating the reporter gene beta-galactosidase in vitro on Cos 7 cells and a CF airway epithelial line (CFTEo approximately ) and ex vivo in a sheep tracheal (s.t.) model. In both cases, transgene expression was significantly (P<0.01) lower at the first time point tested (24 h in vitro, 48 h ex vivo) compared to lipid-#67-mediated gene transfer. However, PLG-mediated expression in vitro was sustained at 48 h, while lipid #67-mediated expression levels had dropped significantly (P<0.05) to 50.3+/-13.7 and 38.2+/-2.7% (Cos 7 and CFTEo approximately cells, respectively) of the 24-h level. This pattern was also seen in the s.t. model where at 72 h, PLG-mediated expression was 125.4+/-7.2% of the 48-h level demonstrating significantly (P<0.05) better retention of transfection efficiency than lipid #67, where levels had fallen to approximately half the 48 h level. By 96 h, expression was still retained in the PLG-transfected group (87.3+/-12.5% of 48 h expression) but was undetectable in the lipid -#67-transfected s.t. Finally, PLG microspheres, encapsulating the reporter gene chloramphenicol transferase (CAT, 80 microg) were instilled intranasally into Balb/C mice. Compared to lipid-#67-mediated delivery, where whole lung CAT expression was highest at 48 h (13.7 x 10(3)+/-0.05 CAT U/microg protein, n=6) and then not detectable at further time points, CAT expression was not detectable in PLG-transfected mice at 48 h, but was detectable at 7, 14 and 21 days after transfection. These data demonstrate that PLG-mediated gene transfer can produce prolonged gene expression in airway epithelia. However, gene transfer efficiency still requires significant improvement.

Non-viral gene transfer therapy for cystic fibrosis

Non-viral methods of gene transfer are being investigated to treat cystic fibrosis (CF) and include naked DNA, lipid-DNA complexes and complexes of DNA with polycations such as poly-L-lysine (poly K) or polyethylenimine (PEI), all of which can carry the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The most recent promising strategy is the use of polycation-DNA complexes, particularly those prepared with poly-K and substituted with polyethylene glycol. These complexes produced partial correction of the CF defect in a mouse model with minimal toxicity, and have advanced to clinical trial. Improvements in this and other non-viral methods are in process and include i). targeting the complexes to the desired cells using receptor ligands, ii). lessening toxicity by changing the mix of lipids or adding protective molecules to polycations, iii). modifying the plasmid DNA to reduce inflammatory CpG sequences and enhance intensity, duration and tissue specificity of expression, and iv). modification of the complexes to improve nuclear access.

Immunological hurdles to lung gene therapy

Gene delivery has the potential to offer effective treatment to patients with life-threatening lung diseases such as cystic fibrosis, alpha1-antitrypsin deficiency and lung cancer. Phase I/II clinical trials have shown that, in principle, gene transfer to the lung is feasible and safe. However, gene expression from both viral and non-viral gene delivery systems has been inefficient. In addition to extra- and intracellular barriers, the host innate and acquired immune system represents a major barrier to successful gene transfer to the lung. Results from studies in experimental animals and clinical trials have shown that inflammatory, antibody and T cell responses can limit transgene expression duration and readministration of the gene transfer vector. We will review here how the development of pharmacological and/or immunological agents can modulate the host immune system and the limitations of these strategies. A better understanding of the immunological barriers which exist in the lung might allow for a more sustained expression of the transgene and importantly help overcome the problem of readministration of viral vectors.

Water-soluble lipopolymer as an efficient carrier for gene delivery to myocardium

Water-soluble lipopolymer (WSLP), which consisted of polyethylenimine (PEI, 1800 Da) and cholesterol, was characterized as a gene carrier to smooth muscle cells and myocardium. Acid-base titration showed that WSLP had a proton-buffering effect. The size of WSLP/plasmid DNA (pDNA) complex was around 70 nm. WSLP/pDNA complex was transfected to A7R5 cells, a smooth muscle cell line. WSLP showed the highest transfection at a 40/1 N/P ratio. WSLP has higher transfection efficiency than PEI (1800 and 25 000 Da), SuperFect, and lipofectamine. In addition, WSLP has less cytotoxicity than PEI (25 000 Da), SuperFect, and lipofectamine. Since WSLP has cholesterol moiety, it may utilize cellular cholesterol uptake pathway, in which low-density lipoprotein (LDL) is involved. An inhibition study with free cholesterol or low-density lipoprotein (LDL) showed that transfection was inhibited by cholesterol or LDL, suggesting that WSLP/pDNA complex is transfected to the cells through the cholesterol uptake pathway. To evaluate the transfection efficiency to myocardium, WSLP/pDNA complex was injected into the rabbit myocardium. WSLP showed higher transfection than PEI and naked pDNA. WSLP expressed the transgene for more than 2 weeks. In conclusion, WSLP is an efficient carrier for local gene transfection to myocardium, and useful in in vivo gene therapy.

Potent inhibition of angiogenesis and liver tumor growth by administration of an aerosol containing a transferrin-liposome-endostatin complex

AIM: To obtain an efficient delivery system for transporting endostatin gene to mouse liver tumor xenografts by administration of aerosol.

METHODS: Recombinant plasmid pcDNA3.0/endostatin containing human endostatin gene together with signal peptide from alkaline phosphatase were transferred into human umbilical vein endothelial cell (HUVEC) by transferrin (TF)-liposome-endostatin complex. Western blot was used to detect the expression of human endostatin in transfected HUVEC cells and its medium. After the tumor-bearing mice were administrated with TF-liposome-endostatin complex, the lung tissue was analyzed by immunohistochemical method for expression of endostatin and the tumors were treated with CD-31 antibody to detect the density of microvesseles in tumor tissues. The inhibition of tumor growth was estimated by the weight of tumors from groups treated with different doses of TF-liposome-endostatin complex. DNA fragmentation assay was used to detect the apoptosis of the cells from primary liver tumor.

RESULTS: Western blot analysis and immunohistochemical method confirmed the expression of endostatin protein in vitro and in vivo. After the tumor sections were treated with CD-31 antibody, the positive reaction cells appeared brown while the negative cells were colorless. The positively stained area of the TF-liposome-endostatin treated group was significantly smaller (P < 0.01, 645.8 ± 5.2 μm²) than that of the control group (1325.4 ± 98.5 μm²). The data showed a significant inhibition of angiogenesis. After administration of TF-liposome-endostatin, comparing with the control group administrated with TF-liposome-pcDNA3.0, liver tumor growth in the mice treated with 50, 250 and 500 mg DNA/kg was inhibited by 36.6%, 40.8%, and 72.8%, respectively (P < 0.01). And a typical DNA fragmentation of apoptosis was found in the cells from tumor tissues of the mice treated with TF-liposome-endostatin but none in the control group.

CONCLUSION: Endostatin gene could be efficiently transported into the mice with TF-liposome-DNA delivery system by administration of aerosol. TF-liposome-mediated endostatin gene therapy strongly inhibited angiogenesis and the growth of mouse xenograft liver tumors. It also could promote the development of apoptosis of tumors without direct influence on tumor cells.

DNA sequences in cationic lipid:pDNA-mediated systemic toxicities

Systemic delivery of synthetic gene transfer vectors such as cationic lipid:plasmid DNA (pDNA) complexes elicits a range of acute physiologic responses, which in the context of therapeutic gene delivery represent dose-limiting toxicities. The most prominent responses are transient leukopenia, thrombocytopenia, serum transaminase elevations, and elevations of proinflammatory cytokines such as interferon-gamma (IFN-gamma), interleukin-12 (IL-12), and tumor necrosis factor-alpha (TNF-alpha). The unmethylated CpG sequences present in plasmid DNA have been implicated as a major cause of the robust cytokine response that follows systemic administration of cationic lipid:pDNA complexes. However, the factors causing the additional significant toxicities (leukopenia, thrombocytopenia, and serum transaminase elevations) recently shown to be associated with vector administration have not been defined. We show here that DNA sequences, such as immune stimulatory CpG sequences, play a significant role in inducing the additional acute toxicities associated with cationic lipid:pDNA complex administration. Importantly, while methylating these CpG sequences results in greatly reduced cytokine levels, this modification does not eliminate their ability to generate the other systemic toxicities. Examples of non-CpG DNA sequences that induce distinct toxicity profiles when administered systemically in the form of cationic lipid:DNA complexes are also identified. Taken together, these results imply that specific DNA sequences are responsible for a significant portion of the systemic toxicities observed after administration of cationic lipid:pDNA complexes.

Current status of gene therapy for inherited lung diseases

Gene therapy as a treatment modality for pulmonary disorders has attracted significant interest over the past decade. Since the initiation of the first clinical trials for cystic fibrosis lung disease using recombinant adenovirus in the early 1990s, the field has encountered numerous obstacles including vector inflammation, inefficient delivery, and vector production. Despite these obstacles, enthusiasm for lung gene therapy remains high. In part, this enthusiasm is fueled through the diligence of numerous researchers whose studies continue to reveal great potential of new gene transfer vectors that demonstrate increased tropism for airway epithelia. Several newly identified serotypes of adeno-associated virus have demonstrated substantial promise in animal models and will likely surface soon in clinical trials. Furthermore, an increased understanding of vector biology has also led to the development of new technologies to enhance the efficiency and selectivity of gene delivery to the lung. Although the promise of gene therapy to the lung has yet to be realized, the recent concentrated efforts in the field that focus on the basic virology of vector development will undoubtedly reap great rewards over the next decade in treating lung diseases.

Aerosol gene therapy

Gene therapy is a novel field of medicine that holds tremendous therapeutic potential for a variety of human diseases. Targeting of therapeutic gene delivery vectors to the lungs can be beneficial for treatment of various pulmonary diseases such as lung cancer, cystic fibrosis, pulmonary hypertension, alpha-1 antitrypsin deficiency, and asthma. Inhalation therapy using formulations delivered as aerosols targets the lungs through the pulmonary airways. The instant access and the high ratio of the drug deposited within the lungs noninvasively are the major advantages of aerosol delivery over other routes of administration. Delivery of gene formulations via aerosols is a relatively new field, which is less than a decade old. However, in this short period of time significant developments in aerosol delivery systems and vectors have resulted in major advances toward potential applications for various pulmonary diseases. This article will review these advances and the potential future applications of aerosol gene therapy technology.

The use of in situ hybridization to study the transgene pathway following cellular transfection with cationic phosphonolipids

Gene therapy is a promising field of research and biotechnological development. Considering their safety and non-immunogenicity, cationic lipids are widely used for gene transfer in vitro and show promise for in vivo gene transfer applications. However, a better understanding of the mechanisms by which transfection occurs and the limiting steps in cellular transfer of foreign DNA are critical for significant improvements of gene transfer. In this work, we have traced the plasmid DNA into human hematopoietic cell line (K562) using the in situ hybridization method in order to define the main difficulties in transfection and to design new agents better adapted to cellular constraints. In this hematopoietic cell line, after showing the efficiency of our synthetic vectors and optimizing their formulation, we observed that only 5 h after transfection the nucleus to cytoplasm signal ratio was three to one, whereas at 24 h it was one to one. In parallel, the level of the reporter protein strongly increased between these times. Those results emphasize the rapidity of transfection and lead one to imagine chemical modifications adjusted to the environment.

An infrared spectroscopic study of the effect of hydration on cationic lipid/DNA complexes

Infrared spectroscopy was used to examine the effect of dehydration on the structure of DNA and cationic lipid/DNA complexes (CLDCs). Information regarding the effect of hydration on the interface between the cationic lipids and DNA was obtained by following subtle but reproducible changes in vibrational bands arising from the DNA bases and phosphate backbone as well as bands from the lipid ester groups within the interfacial region of the bilayer. Dehydration of supercoiled plasmid DNA induces a transition from a B-conformation in solution to a mixed conformation in the dried state. Changes in vibrations of the bases upon drying suggest a change to an A-conformation whereas vibrations from the phosphate moieties suggest A- or C-forms. Vibrational changes in the ribose ring suggest adoption of a C-conformation. When CLDCs composed of either DOTAP (1,2-dioleoyl-3-trimethylammonium-propane) or DDAB (dioctadecyldimethylammonium bromide) cationic lipids with or without equimolar amounts of the helper lipids cholesterol or DOPE (1,2-dioleoylphosphatidylethanolamin) are dried, the DNA is still able to undergo these structural transitions suggesting a nonrigid CLDC structure. The effect of dehydration on these interfacial interactions was found to be dependent on the type of cationic lipid used as well as the type of helper lipid. In addition, this work provides a simple spectroscopic analytical approach that can be used for the characterization of nonviral vectors that has potential pharmaceutical utility.

Barriers to and new approaches for gene therapy and gene delivery in cystic fibrosis

Clinical trials of gene therapy for cystic fibrosis suggest that current levels of gene transfer efficiency are probably too low to result in clinical benefit, largely as a result of the barriers faced by gene transfer vectors within the airways. The respiratory epithelium has evolved a complex series of extracellular barriers (mucus, lack of receptors, immune surveillance, etc.) aimed at preventing penetration of lumenally delivered materials, including gene therapy vectors. In addition, once in the cell, further hurdles have to be overcome, including DNA degradation, nuclear import and the ability to maintain long-term transgene expression. Strategies to overcome these barriers will be addressed in this review and include the use of: (i) clinically relevant adjuncts to overcome the extra- and intracellular barriers; (ii) less-conventional delivery routes, such as intravenous or in utero administration; (iii) more efficient non-viral vectors and 'stealth' viruses which can be re-administered; and (iv) new approaches to prolong transgene expression by means of alternative promoters or integrating vectors. These advances have the potential to improve the efficiency of gene delivery to the airway epithelium, thus making gene therapy a more realistic option for cystic fibrosis.

Development of catheter-based procedures for transducing the isolated rabbit liver with plasmid DNA

Rapid systemic injection of naked plasmid DNA (pDNA) in a large volume into a mouse tail vein has been shown to result in a high level of gene expression in the liver. However, the potential therapeutic benefit to humans embodied in hydrodynamic transfection of the liver cannot be realized until a clinically viable method for gene delivery is developed. In light of this fact, we have devised and evaluated several methods for delivering pDNA to the isolated rabbit liver using minimally invasive catheter-based techniques. Using a lobar technique, pDNA was delivered hydrodynamically to an isolated hepatic lobe using a balloon occlusion balloon catheter to occlude a selected hepatic vein. A whole organ technique was used wherein the entire hepatic venous system was isolated and the pDNA solution injected hydrodynamically into the vena cava between two balloons used to block hepatic venous outflow. Lobar delivery of a plasmid encoding a secreted alkaline phosphatase (SEAP) reporter gene resulted in significant levels of transgene product in the serum. A nonsecreted transgene product, chloramphenicol acetyltransferase (CAT), showed the highest levels of expression in the injected lobe distal to the injection site. Compared to lobar delivery, whole organ delivery yielded much higher serum levels of SEAP expression and a significantly broader hepatic parenchymal distribution of CAT expression. These preliminary studies suggest that catheter-mediated hydrodynamic delivery of pDNA to the isolated liver may provide a method for human gene therapy that is both therapeutically significant and clinically practicable.

Tumor treatment with complexes of cationic lipid and noncoding plasmid DNA results in the induction of cytotoxic T cells and systemic tumor elimination

We have demonstrated recently that treatment of established peritoneal mesothelial tumors with complexes composed of cationic lipid and noncoding plasmid DNA (pNull) results in the inhibition of tumor growth accompanied by the induction of a tumor-specific cellular immune response. In this study, treatment of mice bearing intraperitoneal (i.p.) M3 melanoma tumors with i.p. injections of lipid/pNull complex was found to inhibit tumor growth and induce the development of a cytolytic response against several M3 melanoma-associated antigens. Depletion of CD8(+) T cells, as opposed to natural killer (NK) or CD4(+) T cells, essentially abrogated the therapeutic effect of lipid+pNull complex, thus supporting the involvement of cytotoxic CD8(+) T cells in the antitumor response. The antitumor effect of lipid/pNull complex was maximal following delivery into a tumor-bearing compartment. For example, i.p. delivery of complex was more effective than intravenous (i.v.) or subcutaneous (s.c.) treatment of i.p. M3 tumors. In addition, i.v. injection of complex displayed therapeutic activity against lung metastases caused by i.v. injection of tumor cells, and intratumoral injection of complex into solid s.c. tumors caused regression in most animals. Importantly, the immune response induced by local treatment of tumors with complex also offered systemic protection against tumor cells at distal sites, as illustrated by the eradication of both peritoneal tumors and lung metastases in mice treated with complex delivered i.p. Treatment with lipid/pNull complex, therefore, represents an attractive immune-based treatment modality that could potentially be applied to many tumor types.

Optimisation of real-time quantitative RT-PCR for the evaluation of non-viral mediated gene transfer to the airways

Naked plasmid DNA and DNA/liposome complexes are currently being considered as gene therapy treatments for cystic fibrosis (CF) pulmonary disease. Current methods of gene delivery to the airways result only in transient correction of the CF ion transport defect, and disease treatment is likely to require repeated administrations of vector. However, it is unclear if repeat administration will be tolerated by CF individuals. Technologies including TaqMan (Applied Biosystems) real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) can be used to determine the efficacy of gene transfer formulations. TaqMan RT-PCR assays were designed and optimised to detect plasmid vector-derived and endogenous gene expression. Subsequently, these assays were used to quantify vector-derived mRNA after delivery of naked DNA and DNA/liposome formulations expressing human and murine cystic fibrosis transmembrane conductance regulator (CFTR) to the mouse airways. Vector-derived mRNA was detected in samples following the delivery of naked DNA or DNA/liposomes to the mouse airways, and no reduction in vector-derived mRNA was observed upon repeat administration, a finding that is consistent with the murine and human CFTR being tolerated by the mouse. Although it remains to be seen if CF patients can tolerate long-term expression of wild-type CFTR, these data demonstrate that TaqMan RT-PCR is an effective tool to accurately quantify transgene expression in the airways.

Cytoplasmic deposition of NFkappaB decoy oligonucleotides is insufficient to inhibit bleomycin-induced pulmonary inflammation

Lung inflammation leads to severe tissue destruction and ultimately organ failure in a number of diseases, including cystic fibrosis (CF). The transcription factor nuclear factor kappa B (NFkappaB) regulates expression of many pro-inflammatory mediators. We have assessed the effect of topical administration of NFkappaB decoys in a bleomycin model of acute lung inflammation. Using fluorescein-labelled decoy oligonucleotides (ODN) (80 microg/mouse) we have shown that lipid-complexed and 'naked' ODN transfect conducting airway epithelium in a comparable manner (approximately 65% of cells). However, the ODN were detectable in the cytoplasm, but not in the nucleus of transfected cells. An increase of ODN dose to 500 microg/mouse did not increase nuclear transfection significantly. We determined the effect of cytoplasmic NFkappaB decoys on bleomycin-induced inflammation. We transfected mice with 'naked' decoy and scrambled ODN (500 microg) 1 h before intratracheal administration of bleomycin. We measured IL6 secretion in BALF and lung homogenates and total and differential cell counts in BALF 5 days after bleomycin administration. We did not detect a difference between NFkappaB decoy and scrambled ODN-treated animals in any of the parameters tested. We suggest that access of ODN to the nucleus of airway epithelial cells is a key problem, limiting the efficacy of such decoy strategies, as well as attempts at gene repair.

A versatile linker for nontoxic polyamine-mediated DNA transfection

Low levels of transfection efficacy and lipid-associated cytotoxicity have complicated the use of cationic lipids to facilitate transfer of exogenous DNA to eukaryotic cells. To address these issues, we synthesized a panel of six tetraester polyamines that were designed to minimize cytotoxicity by using pentaerythritol to link the hydrophobic and the DNA-binding domains. We conducted this study to probe the effects of structural modifications around pentaerythritol as a linker on transfection activity and cell viability. We compared polyamines against commercial lipid reagents using luciferase and green fluorescent protein transfection assays in both CHO and NIH3T3 cells. Measurement of transfection activity and cytotoxicity using flow cytometry showed that the more active polyamine analogs exhibited activities comparable to LipofectAMINE PLUS and TransFast. Flow cytometry analyses revealed that all the pentaerythritol-based polyamines were uniformly nontoxic, whereas transfection activity was dependent on headgroup and sidechain composition. These results demonstrate that pentaerythritol is a useful core material for the development of active, nontoxic transfection agents.

Characterization of cationic lipid DNA transfection complexes differing in susceptability to serum inhibition

BACKGROUND

Cationic lipid DNA complexes based on DOTAP (1,2-dioleoyl-3-(trimethyammonium) propane) and mixtures of DOTAP and cholesterol (DC) have been previously optimized for transfection efficiency in the absence of serum and used as a non-viral gene delivery system. To determine whether DOTAP and DC lipid DNA complexes could be obtained with increased transfection efficiency in the presence of high serum concentrations, the composition of the complexes was varied systematically and a total of 162 different complexes were analyzed for transfection efficiency in the presence and absence of high serum concentrations.

RESULTS

Increasing the ratio of DOTAP or DC to DNA led to a dose dependent enhancement of transfection efficiency in the presence of high serum concentrations up to a ratio of approximately 128 nmol lipid/microg DNA. Transfection efficiency could be further increased for all ratios of DOTAP and DC to DNA by addition of the DNA condensing agent protamine sulfate (PS). For DOTAP DNA complexes with ratios of < or = 32 nmol/microg DNA, peak transfection efficiencies were obtained with 4 microg PS/microg DNA. In contrast, increasing the amount of PS of DC complexes above 0.5 microg PS/microg DNA did not lead to significant further increases in transfection efficiency in the presence of high serum concentrations. Four complexes, which had a similar high transfection efficiency in cell culture in the presence of low serum concentrations but which differed largely in the lipid to DNA ratio and the amount of PS were selected for further analysis. Intravenous injection of the selected complexes led to 22-fold differences in transduction efficiency, which correlated with transfection efficiency in the presence of high serum concentrations. The complex with the highest transfection efficiency in vivo consisted of 64 nmol DC/ 16 microg PS/microg DNA. Physical analysis revealed a predicted size of 440 nm and the highest zeta potential of the complexes analyzed.

CONCLUSIONS

Optimization of cationic lipid DNA complexes for transfection efficiency in the presence of high concentrations of serum led to the identification of a DC complex with high transduction efficiency in mice. This complex differs from previously described ones by higher lipid to DNA and PS to DNA ratios. The stability of this complex in the presence of high concentrations of serum and its high transduction efficiency in mice suggests that it is a promising candidate vehicle for in vivo gene delivery.

Biochemical and biophysical characteristics of lipoplexes pertinent to solid tumour gene therapy

Cationic liposomes have become the reagent of choice for transfer of nucleic acids such as plasmids and oligodeoxynucleotides to cells in culture and in vivo. Whilst these reagents have several advantages over other forms of nucleic acid transfer methods, toxicity remains a significant problem, especially in vivo. Recent studies have also highlighted the immunostimulatory nature of these cationic vesicles when complexed to plasmid DNA, a phenomenon that may be harnessed for efficacious usage against tumours. Current research in this dynamic technological field is aimed at the development of cationic lipids that have negligible toxic effects and enhanced transfection capabilities.

Intranasal gene delivery with a polyethylenimine-PEG conjugate

Polyethylenimines (PEIs) are among the most efficient synthetic DNA carriers. High levels of reporter gene expression can be obtained with these agents on a variety of cells. Nevertheless, the gap between their efficiency and that required for therapeutic approaches is still important. With the aim to improve the in vivo transfection properties of PEIs, we have synthesized a conjugate consisting of the linear polymer of 22 kDa covalently modified with polyethyleneglycol (PEG) residues. The resulting conjugate was able to complex DNA and allowed the preparation of highly concentrated polyplexes, in contrast to non-modified PEIs. Administration by nasal instillation of PEI-PEG/DNA complexes in mice resulted in significant levels of transgene expression. Luciferase activity was greatest 24 h after delivery and decreased thereafter. Our results show that the grafting of PEGs can improve some of the properties of PEIs.

Adenovirus-transduced lung as a portal for delivering alpha-galactosidase A into systemic circulation for Fabry disease

Gene therapy efforts have focused primarily on the use of either the liver or skeletal muscle as depot organs for the production of a variety of therapeutic proteins that act systemically. Here we examined the lung to determine whether it could function as yet another portal for the secretion of proteins into the circulation. Fabry disease is caused by a deficiency of the lysosomal hydrolase alpha-galactosidase A, resulting in the abnormal deposition of the glycosphingolipid globotriaosylceramide (GL-3) in vascular lysosomes. Pulmonary instillation of a recombinant adenoviral vector (Ad2/CMVHI-alpha(gal)) encoding human alpha-galactosidase A into Fabry mice resulted in high-level transduction and expression of the enzyme in the lung. Importantly, enzymatic activity was also detected in the plasma, liver, spleen, heart, and kidneys of the Fabry mice. The detection of enzymatic activity outside of the lung, along with the finding that viral DNA was limited to the lung, indicates that the enzyme crossed the air/blood barrier, entered the systemic circulation, and was internalized by the distal visceral organs. The levels of alpha-galactosidase A attained in these tissues were sufficient to reduce GL-3 to basal levels in the lung, liver, and spleen and to approximately 50% of untreated levels in the heart. Together, these results suggest that the lung may be a viable alternate depot organ for the production and systemic secretion of alpha-galactosidase A for Fabry disease.

CpG-depleted plasmid DNA vectors with enhanced safety and long-term gene expression in vivo

Systemic delivery of cationic lipid-plasmid DNA (pDNA) complexes induces an acute inflammatory response with adverse hematologic changes and liver damage. Immunostimulatory CpG motifs in the pDNA are known to contribute substantially to this response. Here we constructed a pDNA vector (pGZB) that has been depleted of 80% of the CpG motifs present in the original vector. Compared with the unmodified vector, systemic administration of pGZB induced considerably fewer changes in blood parameters, reduced levels of inflammatory cytokines, and decreased liver damage. Despite the extensive sequence modifications within pGZB, there were still robust levels of transgene expression. Furthermore, in contrast to the transient expression observed from the unmodified vector, we observed sustained or increasing expression for up to 49 days from pGZB in the lung and liver of immunocompetent BALB/c mice. Studies adding CpG motifs in trans or in cis indicate that the reduced CpG content of pGZB was the major determinant for its persistent expression. This combination of decreased toxicity and sustained expression suggests that CpG-depleted pDNA vectors can greatly improve the safety and efficacy of synthetic gene delivery systems.

Isolation of plasmid DNA from cell lysates by aqueous two-phase systems

This work presents a study of the partitioning of a plasmid vector containing the cystic fibrosis gene in polyethylene glycol (PEG)/salt (K2HPO4) aqueous two-phase systems (ATPS). The plasmid was extracted from neutralized alkaline lysates using PEG with molecular weights varying from 200 to 8000. The effects of the lysate mass loaded to the ATPS (20, 40, and 60% w/w) and of the plasmid concentration in the lysate were evaluated. The performance of the process was determined by qualitative and quantitative assays, carefully established to overcome the strong interference of impurities (protein, genomic DNA, RNA), salt, and PEG. Plasmid DNA partitioned to the top phase when PEG molecular weight was lower than 400. The bottom phase was preferred when higher PEG molecular weights were used. Aqueous two-phase systems with PEG 300, 600, and 1000 were chosen for further studies on the basis of plasmid and RNA agarose gel analysis and protein quantitation. The recovery yields were found to be proportional to the plasmid concentration in the lysate. The best yields (>67%) were obtained with PEG 1000. These systems (with 40 and 60% w/w of lysate load) were able to separate the plasmid from proteins and genomic DNA, but copartitioning of RNA with the plasmid was observed. Aqueous two-phase systems with PEG 300 concentrated both plasmid and proteins in the top phase. The best system for plasmid purification used PEG 600 with a 40% (w/w) lysate load. In this system, RNA was found mostly in the interphase, proteins were not detected in the plasmid bottom phase and genomic DNA was reduced 7.5-fold.

Characterisation of LMD virus-like nanoparticles self-assembled from cationic liposomes, adenovirus core peptide mu and plasmid DNA

Liposome:mu:DNA (LMD) is a ternary nucleic acid delivery system built around the mu peptide associated with the condensed core complex of the adenovirus. LMD is prepared by precondensing plasmid DNA (D) with mu peptide (M) in a 1:0.6 (w/w) ratio and then combining these mu:DNA (MD) complexes with extruded cationic liposomes (L) resulting in a final lipid:mu:DNA ratio of 12:0.6:1 (w/w/w). Correct buffer conditions, reagent concentrations and rates of mixing are all crucial to success. However, once optimal conditions are established, homogeneous LMD particles (120 +/- 30 nm) will result that each appear to comprise an MD particle encapsulated within a cationic bilammellar liposome. LMD particles can be formulated reproducibly, they are amenable to long-term storage (>1 month) at -80 degrees C and are stable to aggregation at a plasmid DNA concentration up to 5 mg/ml (15 mM nucleotide concentration). Furthermore, LMD transfections are significantly more time and dose efficient in vitro than cationic liposome-plasmid DNA (LD) transfections. Transfection times as short as 10 min and plasmid DNA doses as low as 0.001 microg/well result in significant gene expression. LMD transfections will also take place in the presence of biological fluids (eg up to 100% serum) giving 15-25% the level of gene expression observed in the absence of serum. Results from confocal microscopy experiments using fluorescent-labelled LMD particles suggest that endocytosis is not a significant barrier to LMD transfection, although the nuclear membrane still is. We also confirm that topical lung transfection in vivo by LMD is at least equal in absolute terms with transfection mediated by GL-67:DOPE:DMPE-PEG(5000) (1:2:0.05 m/m/m), an accepted 'gold-standard' non-viral vector system for topical lung transfection, and is in fact at least six-fold more dose efficient. All these features make LMD an important new non-viral vector platform system from which to derive tailor-made non-viral delivery systems by a process of systematic modular upgrading.

Novel water insoluble lipoparticulates for gene delivery

PURPOSE

The objective was to design and prepare water insoluble lipoparticulates (ISLPs) for efficient gene delivery to lung tissue.

METHODS

Nona[(ethylenimine)-co-[(2-aminoethyl)-N-choleseteryl-oxycarbonyl-ethylenimine]] (NEACE-T) was synthesized in both its free-base and chloride salt-forms using linear polyethylenimine (PEI, Mw 423) as a headgroup and cholesteryl chloroformate as a hydrophobic lipid anchor resulting in a T-shaped lipononamer. Semitelechelic N(alpha)-cholesteryloxycarbonyl nona(ethylenimine) (st-NCNEI-L) was synthesized similarly resulting in a linear lipononamer. As confirmed by 1H-NMR, the site of conjugation was either a primary amine resulting in a linear configuration (st-NCNEI-L) or a secondary amine resulting in a T-shaped configuration (NEACE-T). ISLPs were prepared by combining NEACE-T or st-NCNEI-L with a co-lipid, 2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) at 1/1, 1/2, and 2/1 molar ratios and the lipoparticulates were hydrated and filtered. ISLP/p2CMVmIL-12 complexes were characterized for particle size, zeta potential, surface morphology, cytotoxicity, and in vitro transfection efficiency.

RESULTS

Transgene expression was dependent on the site of cholesterol conjugation, lipononamer:colipid molar ratio, and ISLP/ p2CMVmIL-12 charge ratios. ISLP/p2CMVmIL-12 complexes were nontoxic to murine colon adenocarcinoma (CT-26) cells at 9/1 (+/-) or lower, had a mean particle size of 330-400 nm while the zeta potential varied from 36-39 mV. Atomic force microscopy (AFM) showed the surface morphology to be that of an oblate spheroid with a size comparable to that determined by dynamic light scattering. ISLP/ p2CMVmIL-12 complexes prepared using free-base NEACE-T:DOPE (1/2) at charge ratios of 3/1 and 5/1 (+/-) provided the highest levels of transgene expression, 18 times more than the levels provided by the salt-form. Secreted levels of mIL-12 p70 were 75 times higher for ISLP/p2CMVmIL-12 complexes than naked p2CMVmIL-12 and nearly 4 times higher than PEI 25 kDa/p2CMVmIL-12 complexes.

CONCLUSIONS

The transfection efficiency of the ISLPs was dependent on the site of cholesterol conjugation, amount of colipid, and charge ratio. The highest levels of transgene expression were provided by NEACE-T:DOPE (1/2)/p2CMVmIL-12 at a 3/1 (+/-) charge ratio.

Bilamellar cationic liposomes protect adenovectors from preexisting humoral immune responses

Adenoviral vectors have been widely used for gene therapy, but they are limited both by the presence of a humoral immune response that dramatically decreases the level of transduction after reinjection and by their requirement for target cells to express appropriate receptors such as Coxsackie adenovirus receptor (CAR). To overcome both limits, we encapsulated adenovectors using bilamellar DOTAP:chol liposomes. Electron micrography (EM) showed that these liposomes efficiently encapsulated the vectors, allowing CAR-independent adenovector transduction of otherwise resistant cells. DOTAP:chol-encapsulated adenovectors encoding LacZ or alpha(1)-antitrypsin inhibitor (AAT) were also functionally resistant ex vivo and in vivo to the neutralizing effects of human anti-adenoviral antibodies, unlike other liposomal systems. Hence, bilamellar DOTAP:chol liposomes may be useful for applications using adenovectors in which the target cells lack adenoviral receptors or in which the recipient already has or develops a neutralizing antibody response that would otherwise inactivate readministered vector.

Anchor-dependent lipofection with non-glycerol based cytofectins containing single 2-hydroxyethyl head groups

Detailed structure-activity investigations aimed at probing the anchor chain length dependency for glycerol-based lipofectins have been reported previously. Herein, we report on the first detailed investigation on the anchor-dependent transfection biology of non-glycerol based simple monocationic cytofectins containing single 2-hydroxyethyl head group functionality using 11 new structural analogs of our previously published first generation of non-glycerol based transfection lipids (lipids 1-11). The C-14 and C-16 analogs of DOMHAC (lipids 4 and 5, respectively) were found to be remarkably efficient in transfecting COS-1 cells. In addition, the present anchor-dependency investigation also revealed that the C-14 analog of DOHEMAB (lipid 10) is significantly efficient in transfecting both COS-1 and NIH3T3 cells. Our results also indicate that too strong lipid-DNA interactions might result in weaker transfection for non-glycerol based cationic lipids. In summary, the anchor-dependence investigations presented here convincingly demonstrate that non-glycerol based cationic lipids containing a single hydroxyethyl head group and hydrophobic C-14 or C-16 anchors are promising non-toxic cationic transfection lipids for future use in liposomal gene delivery.

A simple method to overcome the interference of hemoglobin in the detection of reporter genes in vivo

The determination of chemiluminescent intensity of reporter gene expression in vivo is generally disturbed by the presence of hemoglobin. Current methods consist in using perfusion to eliminate blood from investigated tumors or organs. In this work we propose a simple method to overcome this difficulty. The method consists in establishing an absorbance-dependence plot of the ratio R% = phi/phi(0) between the chemiluminescent intensities measured when hemoglobin is present or absent. For every measurement of the luminescent intensity phi on sample containing blood, if the absorbance A of the hemoglobin is determined, it allows one to have the intensity ratio R% which in turn gives the corrected intensity phi(0) when the absorption by hemoglobin is eliminated. The method is particularly adapted for comparative measurements of transfection levels in tumors where perfusion cannot be easily performed.

Non-viral gene delivery to atelectatic and ventilated lungs

BACKGROUND

Three different nonviral vectors and naked DNA were evaluated for in vivo transfer of plasmid DNA to rat lungs through airways in either atelectatic or ventilated lungs.

METHODS

The F344 rats underwent instillation of 300 microg DNA (pCIluc, luciferase) to the left lung. Naked DNA, linear polyethylenimine, branched polyethylenimine, and lipid GL-67 (in either atelectatic or ventilated lungs) were assessed (n = 5 per group). After 24 hours, left lung PaO2 (mm Hg) and luciferase activity (RLU/mg) were measured. The median (range) was given, and the analysis of variance was applied, followed by the planned comparison on log-transformed data.

RESULTS

In atelectatic lungs, lipid GL-67 was best (927 [330 to 4112] RLU/mg; p < 0.001 versus other groups of atelectatic lung; p < 0.001 versus all other groups), but highest luciferase activity in all groups was measured in ventilated lungs using linear polyethylenimine (1,240 [922 to 2519] RLU/mg; p < 0.001 versus other groups of ventilated lung; p < 0.001 versus all other groups). In comparison with naked DNA, all nonviral vector systems significantly impaired PaO2 24 hours after airway transfection (p < 0.001; naked DNA versus all other groups). Regardless of transfection technique, PaO2 was worst in lungs transfected by linear polyethylenimine.

CONCLUSIONS

Highest transfection was achieved with GL-67 in atelectatic lungs and with linear polyethylenimine in ventilated lungs. All gene delivery systems impaired gas exchange of the transduced lung in comparison with naked DNA.

The nasal epithelium as a factory for systemic protein delivery

We have previously shown that recombinant Sendai virus (SeV) produces efficient in vivo airway epithelial gene transfer. The ability to produce therapeutic levels of circulating proteins following noninvasive gene transfer would have widespread clinical application. Here, we compared nose, lung, and skeletal muscle for the ability to produce circulating levels of the secreted mouse antiinflammatory cytokine interleukin-10 (IL10) following SeV-mediated gene transfer. High levels of serum IL10 were obtained from each site with a potency order of lung > nose > muscle for a given viral titer. Serum levels from each site were within the likely required range for anti-inflammatory effects. The combination of a high-efficiency gene transfer agent (SeV) and sites that can be assessed noninvasively (nose or lung) may circumvent several current challenges to gene therapy.

Nonviral vector for efficient gene transfer to human ovarian adenocarcinoma cells

OBJECTIVE

Various strategies have been attempted to design efficient protocols for ovarian cancer gene therapy but there has been little progress in their clinical application. In this study, we formulated and evaluated a new cationic liposome prepared with dioleoyltrimethylaminopropane (DOTAP), 1,2-dioleoyl-3-phosphophatidylethanolamine (DOPE), and cholesterol (Chol) (DDC) for plasmid DNA transfer into ovarian cancer cells.

METHOD

The DDC liposome was prepared by mixing the DOTAP:DOPE:Cholin a 1:0.7:0.3 molar ratio using the extrusion method. Plasmid DNA (pEGFP-C1) and DDC were complexed at various weight ratios to find the optimum condition and the percentage of transfected cells was determined by selecting a green fluorescence protein (GFP) expressing cells in flow cytometry. The transfection efficiency of the DDC liposome was compared with 3[N-(N,N-dimethylaminoethylene) carbamoyl] cholesterol (DC-Chol)/DOPE liposome and commercially available lifopectin.

RESULTS

The optimal transfection of plasmid DNA was achieved at a 1:4 (w/w) ratio of DDC to DNA. The DDC/DNA complex exhibited higher transfection efficiency in human ovarian cancer cells (OVCAR-3 and SK-OV-3 cells) compared to that in other types of cell lines (NCI-NIH:522 and HepG2 cells). Flow cytometric analysis revealed that the DDC/DNA complex exhibited an over fourfold increase in GFP expression levels compared with DC-Chol/DOPE or lipofectin in OVCAR-3 cells. This result was further confirmed by confocal microscopy and RT-PCR analysis.

CONCLUSION

These results suggest that our newly formulated cationic liposome (DDC) appears to be a promising nonviral vector for treating ovarian adenocarcinoma because of its selective high gene transfer ability in ovarian cancer cells.

Novel non-glycerol-based cytofectins with lactic acid-derived head groups

We report herein the design, synthesis, and transfection biology of a novel series of non-glycerol-based cationic lipids with lactic acid-derived head groups The synthetic procedure adopted herein for preparing 1-hydroxy-prop-2-yl head-group-based monocationic transfection lipids 1-7 is fairly straightforward and potentially applicable in designing other cationic lipids with lactic acid-derived head groups. A striking anchor-length dependency was observed in NIH3T3 cells in the sense that except lipid 4, all the other lipids were essentially transfection-inefficient. Ethidium bromide assay for the lipid:DNA interactions is consistent with the general observation that significant lipid:DNA interactions do not guarantee on improved transfection efficiency cationic lipid mediated gene delivery. Given its remarkable transfection properties and low cellular toxicity, lipid 4 is likely to find future use in the area of liposomal gene delivery.

Therapeutic success and efficacy of nonviral liposomal cDNA gene transfer to the skin in vivo is dose dependent

It is well documented that responses to growth factor treatment typically display bell-shaped dose responses that can significantly affect efficacy. Here we tested the hypothesis that nonviral liposomal gene delivery also displays this characteristic. We chose two different growth factors, keratinocyte growth factor (KGF) and insulin-like growth factor-I (IGF-I) CMV-driven transfecting constructs at three different concentrations and assessed efficacy on several physiological parameters that are descriptive of wound healing progress in a burn-wound healing model. Rats were given a 60% TBSA scald burn and randomly divided into one of seven groups to receive weekly subcutaneous injections of liposomes containing the cDNA for KGF (0.2 microg, 2.2 microg, or 22.2 microg), or liposomes containing the cDNA for IGF-I (0.2 microg, 2.2 microg, or 22.2 microg) at various concentrations, but constant liposome:DNA ratios and a LacZ gene (0.2 microg) CMV-driven construct for beta-galactosidase as vehicle and marker gene. Transfection was confirmed by histology for beta-galactosidase. Physiological efficacy was evaluated by measuring the wound healing parameters that define dermal and epidermal regeneration. Transfection products were found in the cytoplasm of rapidly dividing cells of the granulation tissue. Different doses of the nonviral cDNA gene transfer coding for KGF or IGF-I resulted in different outcomes for dermal and epidermal regeneration. There was a dose-dependent response to both growth factor gene transfers that was not dissimilar from that typically displayed by treatment with growth factor proteins. Both concentrations below and above the optimal concentration of DNA:liposomal preparations did not yield the results observed at the optimal concentration.

Towards a rational development of anti-endotoxin agents: novel approaches to sequestration of bacterial endotoxins with small molecules

Endotoxins, or lipopolysaccharides (LPS), present on the surface of Gram-negative bacteria, play a key role in the pathogenesis of septic shock, a common clinical problem and a leading cause of mortality in critically ill patients, for which no specific therapeutic modalities are available at the present time. The toxic moiety of LPS is a glycolipid called 'lipid A', which is composed of a bisphosphorylated diglucosamine backbone bearing up to seven acyl chains in ester and amide linkages. Lipid A is structurally highly conserved in Gram-negative bacteria, and is therefore an attractive target for developing anti-endotoxin molecules designed to sequester, and thereby neutralize, the deleterious effects of endotoxins. The anionic and amphipathic nature of lipid A enables the interaction of a wide variety of cationic amphiphiles with the toxin. This review describes the systematic evaluation of several structural classes of cationic amphiphiles, both peptides and non-peptidic small molecules, in the broader context of recent efforts aimed at developing novel anti-endotoxin strategies. The derivation of a pharmacophore for LPS recognition has led to the identification of novel, nontoxic, structurally simple small molecules, the lipopolyamines. The lipopolyamines bind and neutralize LPS in in vitro experiments as well as in animal models of endotoxicity, and thus present novel and exciting leads for rational, structure-based development of LPS-sequestering agents of potential clinical value.

Antitumor activity of cationic lipid complexed with immunostimulatory DNA

We previously reported that treatment of intraperitoneal tumors with complexes of cationic lipid and noncoding plasmid DNA leads to the development of a specific, cytotoxic T-cell response correlating with the rejection of established tumor cells as well as subsequent tumor re-challenge. Here, focusing on an intraperitoneal AB12 mesothelioma model, we show that the anticancer effects of the lipid:DNA complex are associated with DNA containing immunostimulatory CpG motifs. Complexes prepared with cationic lipid and bacterial plasmid DNA, Escherichia coli genomic DNA fragments, or synthetic immunostimulatory CpG oligodeoxynucleotides provided a substantial survival benefit, whereas eukaryotic DNA and methylated bacterial DNA had little or no therapeutic activity. Alternative inflammatory stimuli such as thioglycolate, poly(I:C), and incomplete or complete Freund's adjuvant failed to reproduce the antitumor activity obtained with the lipid:DNA complex. The innate immune response triggered by lipid:DNA complexes led to the development of a systemic immune response against tumor cells that allowed animals to reject tumors not only at the intraperitoneal treatment site, but also at a distal subcutaneous site. These data demonstrate that immunostimulatory DNA complexed with cationic lipid is a potent inducer of innate and adaptive immune responses against tumor cells and represents a potentially useful tool in the immunotherapy of cancers for which tumor-associated antigens have not been identified.

Increased persistence of lung gene expression using plasmids containing the ubiquitin C or elongation factor 1alpha promoter

For effective gene therapy of chronic disease, persistent transgene expression at therapeutic levels is required. Clinical studies of airway gene transfer in patients with cystic fibrosis (CF) have resulted in short-lived transgene expression. We used intra-nasal dosing of naked plasmid DNA to the murine lung as a model for investigating the duration of airway gene transfer from a series of reporter expression plasmids. Transgene expression was transient when mediated by the viral promoters CMV, RSV and SV40, falling to less than 10% of peak expression after 2 weeks, although the presence of the adenoviral E4ORF3 gene in cis, resulted in extended duration of reporter activity from the CMV promoter. Transient expression from these promoters was not due to loss of the vector as determined by quantitative TaqMan PCR analysis. However, use of the promoters from the human polybiquitin C (UbC) and the elongation factor 1alpha (EF1alpha) genes resulted in persistent gene expression in the mouse lung. The UbC promoter directed high-level reporter activity which was maintained for up to 8 weeks and was still detectable 6 months after a single administration. Such persistent airway transgene expression from a nonviral vector without the concomitant expression of a potential antigen has not been reported previously. Thus, despite the persistence of vector DNA in vivo, attenuation of promoter function may lead to silencing of transgene expression and careful selection of promoter sequences is recommended for in vivo gene transfer.

Mucus altering agents as adjuncts for nonviral gene transfer to airway epithelium

Nonviral vectors have been shown to be a safe and valid alternative to recombinant viruses for gene therapy of cystic fibrosis (CF). Nevertheless, gene transfer efficiency needs to be increased before clinical efficacy is likely in man. One barrier to increased efficacy is normal airway mucus. Using an ex vivo model of sheep tracheal epithelium, we show that this barrier can, in part, be overcome by treatment with the mucolytic agents, Nacystelyn or N-acetylcysteine using either a cationic lipid or a cationic polymer as the gene transfer agent. Further, in vivo application of either Nacystelyn or the anticholinergic glycopyrrolate, both clinically used agents, resulted in increased reporter gene expression in the mouse lung, but no significant correction of the bioelectric defect in CF null mice. These results, whilst unlikely to be sufficient in themselves to achieve clinically relevant gene therapy, may be a further useful step in the attainment of this goal.

Use of perfluorocarbon (fluorinert) to enhance reporter gene expression following intratracheal instillation into the lungs of Balb/c mice: implications for nebulized delivery of plasmids

Perfluorocarbons combine high respiratory gas dissolving capabilities with extreme chemical and biological inertness and therefore offer an attractive option as an excipient in the area of pulmonary therapeutics. Perfluorocarbons have also been shown to "float" mucus, because of their high densities (1.9-2.5 g/mL), which may hold potential in gene delivery for cystic fibrosis patients, in terms of enhancing penetration through highly viscous mucus and thereby providing access to target epithelial cells to correct the gene defect. Additionally, their low surface tension allows for better dispersion. A commonly available perflurocarbon, heptacosafluorotributylamine (Fluorinert), was used to deliver either plasmid DNA (pDNA) alone or cationic-lipid-complexed plasmid DNA to the lungs of Balb/c mice by direct intratracheal instillation. The complexes consisted of supercoiled (SC) plasmid DNA (4.7 Kb, 0.625 mg/mL) and lipid (ethyldimyristoyl phosphatidylcholine [EDMPC]/cholesterol [1:1 mole ratio], with pDNA (3:1 mg pDNA/mM EDMPC in 20 mM Tris-HCl pH 8.0) expressing chloramphenicol acetyl transferase (CAT) or beta-galactosidase (beta-Gal). pDNA alone was supplemented with 14% w/v Fluorinert. Cationic lipid/pDNA complexes were supplemented with 3, 8, and 14% w/v Fluorinert. Results showed that the CAT expression from pDNA alone was enhanced 24 x using 14% w/v Fluorinert, whereas that from the cationic-lipid-formulated pDNA was enhanced 7 x using 14% w/v Fluorinert. Immunohistochemistry showed that beta-Gal expression was primarily from epithelial cells and not from F4/80 or MAC3 antigen-stained cells (predominantly macrophages), indicating efficient delivery.

Inhalation therapy: new delivery systems

The objective of this article is to provide an overview of recent advances in inhalation drug delivery. Problems, advantages, limitations, and developments encountered by different inhalation devices and the agents used in these for the purpose of pulmonary delivery are discussed. A critical appraisal is presented and finally the future directions especially in research of the inhaled therapeutics and aerosols are described.

Sterically stabilized BGTC-based lipoplexes: structural features and gene transfection into the mouse airways in vivo

BACKGROUND

Colloidal stability of lipid/DNA aggregates is a major requirement for cationic lipid-mediated transfection which is particularly difficult to fulfil at the high DNA concentrations used for in vivo gene delivery. Thus, we have investigated the potential of poly(ethyleneglycol) (PEG) conjugates for steric stabilization of lipoplexes formed by bis(guanidinium)-tren-cholesterol/dioleoyl phosphatidylethanolamine (BGTC/DOPE) liposomes, a class of cationic liposomes we have developed over the past few years.

METHODS AND RESULTS

We demonstrate that adequate lipophilic PEG derivatives can stabilize BGTC/DOPE lipoplexes formed at high DNA concentration. We also report the results of cryotransmission electron microscopy studies indicating that PEG-stabilized lipoplexes form DNA-coated structures which assemble into clusters exhibiting various complex morphologies. Finally, we report data from in vivo transfection experiments suggesting that PEG-mediated colloidal stabilization of concentrated lipoplex solutions may allow enhanced transfection of the mouse airways via intranasal administration.

CONCLUSION

Our results represent an important step towards the design of multimodular BGTC-based systems for improved in vivo gene transfection.

Aerosolization of cationic lipid-DNA complexes: lipoplex characterization and optimization of aerosol delivery conditions

This study deals with the development of gene therapy in the treatment of lung diseases. It reports on the use of ultrasonic nebulization to administer plasmid-lipid complexes to the lungs of mice to transfect their epithelial cells. A plasmid complexed to cationic lipids was aerosolized using an ultrasonic nebulizer. We then characterized the lipoplex size and visualized the lipoplex by electron microscopy. Finally, we assessed the in vivo transgene expression in the lungs further to the aerosolization of different lipid-plasmid formulations. The nebulizer-generated particles were small and looked like a string composed of little and more or less cubic units. Transgene expression was detected in the lungs of mice further to a 20-min exposure to aerosol particles produced with the ultrasonic nebulizer. The results obtained with our optimized plasmid-lipid-NaCl formulation suggest that this route can be used to administer an appropriate gene to the airways for the treatment of respiratory disorders.